a. Field of the Invention
The current invention relates to portable storage tanks.
b. Background of the Invention
Large tanks are currently provided for storing and dispensing fluids such as fracturing liquids, drilling muds and the like for use at a gas or oil well site. Such tanks are also used to receive and hold fluids and chemicals at industrial plants. They are also used on environmental clean-up jobs as well as spills to hold fluids until they can be properly disposed of. When empty, these tanks are towed by truck from one site to another where they are refilled and reused.
When an oil well is brought into production, it will generally produce salt water as well as oil and natural gas. It is common practice to separate the gas from the liquids, and to separate the oil from the salt water. The oil and saltwater are stored in separate tanks of a tank battery placed at the oil well site. The oil is sold from tanks within the tank battery and the salt water is temporarily stored so that it can be subsequently disposed of without harming the environment.
One type of tank which has been used to store oil and salt water has been constructed in the form of a cylinder. This shape exploits the rigidity of a cylindrical structure against hydro-static pressure by liquids within the tank. With this shape, the volume of the oil in the tank is proportional to the depth of the oil in the tank. Because of this proportionality, the oil buyer can determine the quantity of oil he has purchased by measuring the change in depth in the tank and applying an appropriate conversion factor. However, construction of cylindrical tanks involves the bending of plate metal into curved sections.
For transportation purposes, the width of a cylindrical tank is its diameter, and the diameter is fixed by the height and volume of the tank. As a result, cylindrical tanks will often present a wide load to be transported. Similarly, cylindrical tanks cannot be packed together into a compact load because of the curvature of their surfaces. As a result, portable cylindrical tanks have been transported to oil fields as individual units, which are then individually placed and connected with other tanks and to the well prior to use. The inter-connection of the tanks can involve cutting pipe to length and threading the ends of the pipe for screw connections.
Sometimes a well will not produce oil in sufficient quantity for the continuation of production from the well in a commercial fashion. When this occurs, not only is the initial cost of transporting the tank battery to the well and placing the tank battery for production lost, but additional cost is incurred in dismantling the tank battery and transporting the tanks from the site of the well to a new location.
Portable rectangular tanks have also been developed and used in the oil industry. These tanks usually have lengths of 30 to 40 feet, a height of from approximately 9 to 12 feet and a width of 8 feet. These tanks are usually transported as trailers behind trucks. Various state and local highway ordinances limit the size of these trailers for over-the-road transport, but these tanks can be made such that special oversize load permits are not needed for transportation. Placing the rectangular tanks side by side allows for more standard pipe distances when a tank battery is set up. Rectangular tanks can be set up side by side, with little space between tanks, so space is efficiently used within a tank battery.
Frequently, these tanks will he rented, where the user pays rent for each tank in use. If larger tanks were provided, the user would be able to rent fewer tanks for a possible cost savings. Also, certain operational and maintenance tasks are required for each tank, so having fewer overall tanks would reduce these operational and maintenance tasks. These tanks are constructed to hold a large capacity, but Department of Transportation (DOT) requirements, manufacturing factors, customs, and other factors tend to limit the maximum tank volume.